Cardiac arrhythmia treatment methods

ABSTRACT

Disclosed are methods of preventing or treating cardiac arrhythmia. In one embodiment, the methods include administering to an amount of at least one polynucleotide that modulates an electrical property of the heart. The methods have a wide variety of important uses including treating cardiac arrhythmia.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional ApplicationNo. 60/230,311 filed on Sep. 6, 2001, and U.S. Provisional ApplicationNo. 60/295,889, filed on Jun. 5, 2001, the disclosure of which are bothincorporated herein by reference.

STATEMENT OF FEDERALLY SPONSORED RESEARCH

Funding for the present invention was provided is part by the Governmentof the United States by virtue of Grant No. NIH P50 HL52307 by theNational Institutes of Health. Thus, the Government of the United Stateshas certain rights in and to the invention claimed herein.

FIELD OF THE INVENTION

The invention generally features methods for the prevention or treatmentof heart arrhythmia. Preferred, methods generally involve administeringat least one therapeutic polynucleotide to a mammal sufficient tomodulate at least one electrical property of the heart. Modulation ofthe electrical property addresses the arrhythmia typically byencouraging normal heart electrical function.

BACKGROUND

The mammalian heart is understood to maintain an intrinsic rhythm bycreating electric stimuli. Generally, the stimuli form a depolarizationwave that propagates within specialized cardiac conducting tissue andthe myocardium. The usually well-ordered wave movement facilitatescoordinated contractions of the myocardium. These contractions are theengine that moves blood throughout the body. See generally The Heart andCardiovascular System, Scientific Foundations. (1986) (Fozzard, H. A. etal. eds) Raven Press, NY.

Under most circumstances, cardiac stimuli are controlled by recognizedphysiological mechanisms. However there has been long-standingrecognition that abnormalities of excitable cardiac tissue can lead toabnormalities of the heart rhythm. These abnormalities arc generallyreferred to as arrhythmias. Most arrhythmias are believed to stem fromdefects in cardiac impulse generation or propagation that cansubstantially compromise homeostasis, leading to substantial patientdiscomfort or even death. For example, cardiac arrhythmias that causethe heart to beat too slowly are known as bradycardia, orbradyarrhythmia. In contrast, arrhythmias that cause the heart to beattoo fast are referred to tachycardia, or tachyarrhythmia. See generallyCardiovascular Arrhythmias (1973) (Dreifus, L. S. and Likoff, W. eds)Grune & Stratton, NY.

The significance of these and related heart disorders to public healthcannot be exaggerated. Symptoms related to arrhythmias range fromnuisance, extra heart beats, to life-threatening loss of consciousness.Complete circulatory collapse has also been reported. Morbidity andmortality from such problems continues to be substantial. In the UnitedStates alone for example, cardiac arrest accounts for 220,000 deaths peryear. There is thought to the more than 10% of total American deaths.Atrial fibrillation, a specific form of cardiac arrhythmia, impacts morethan 2 million people in the United States. Other arrhythmias accountfor thousands of emergency room visits and hospital admissions eachyear. See eg., Bosch, R. et al. (1999) in Cardiovas. Res. 44: 121 andreferences cited therein.

Cardiac electrophysiology has been the subject of intense interest.Generally, the cellular basis for all cardiac electrical activity is theaction potential (AP). The AP is conventionally divided into five phasesin which each phase is defined by the cellular membrane potential andthe activity of potassium, chloride, and calcium ion channel proteinsthat affect that potential. Propagation of the AP throughout the heartis thought to involve gap junctions. See Tomaselli, G. and Marban, E.(1999) in Cardiovasc. Res. 42: 270 and references cited therein.

There have been limited attempts to treat cardiac arrhythmias andrelated heart disorders.

Specifically, many of the past attempts have beers confined topharmacotherapy, radiofrequency ablation, use of implantable devices,and related approaches. Unfortunately, this has limited options forsuccessful patient management and rehabilitation.

In particular, radiofrequency ablation has been reported to address alimited number of arrhythmias eg., atrioventricular (AV) node reentrytachycardia, accessory pathway-mediated tachycardia, and atrial flutter.However, more problematic arrhythmias such as atrial fibrillation andinfrared-related ventricular tachycardia, are less amenable to this andrelated therapies. Device-based therapies (pacemakers anddefibrillators, for instance) have been reported to be helpful for somepatients with bradyarrhythmias and lifesaving for patients withtachyarrhythmias. However, such therapies does not always preventtachyarrhythmias. Moreover, use of such implementations is most oftenassociated with a prolonged commitment to repeated procedures,significant expense, and potentially catastrophic complicationsincluding infection, cardiac perforation, and lead failure.

Drug therapy remains a popular route for reducing some arrhythmicevents. However, there has been recognition that systemic effects areoften poorly tolerated. Moreover, there is belief that proarrhythmictendencies exhibited by many drugs may increase mortality in manysituations. See generally Bigger J. T and Hoffman, B. F. (1993) in ThePharmacological Basis of Therapeutics 8^(th) Ed. (Gilman, A. G et al.eds) McGraw-Hill, NY and references cited therein.

It would be desirable to have more effective methods for treating orpreventing cardiac arrhythmias. It would be especially desirable to havegene therapy methods for treating or preventing such arrhythmias.

SUMMARY OF THE INVENTION

The present invention provides methods of preventing or treating cardiacarrhythmia in a mammal. In general, the methods involve administering tothe mammal at least one polynucleotide that preferably modulates atleast one electrical property of the heart. Use of the polynucleotidesaccording to the invention modulates the heart electrical property,thereby preventing or treating the cardiac arrhythmia.

There has been a long-felt need for more effective anti-arrhythmictherapies. The invention addresses this need by providing, for the firsttime, therapeutic methods for administering one or more therapeuticpolynucleotides to the heart under conditions sufficient to modulate(increase or decrease) at least one heart electrical property. Preferreduse of the invention modulates heart electrical conduction preferablyreconfigures all or part of the cardiac action potential (AP). That usehelps achieve a desired therapeutic outcome. Significant disruption ofnormal electrical function is usually reduced and often avoided by thepresent methods. Moreover, use of the invention is flexible andprovides, also for the first time, important anti-arrhythmic strategiesthat can be tailored to the health requirements of one patient orseveral as needed.

The invention provides other advantages that have been heretobeforedifficult or impossible to achieve. For example, and unlike priorpractice, the invention methods are genetically and spatiallycontrollable ie., they provide for administration of at least onepre-defined polynucleotide to an identified heart tissue or focal area.Since there is recognition that many protein encoding polynucleotidescan be expressed successfully in heart tissue, the invention is agenerally applicable anti-arrhythmia therapy that can be employed tosupply the heart with one or a combination of different therapeuticproteins encoded by the polynucleotides. Such proteins can be providedtransiently or more long-term as needed to address a particular cardiacindication.

The invention provides further benefits and advantages. For example,practice of prior anti-arrythmic approaches involving pharmacotherapy,radiofrequency ablation, and implantable device approaches is reducedand oftentimes eliminated by the invention. Moreover, the inventionprovides, highly localized gene delivery. Importantly, treated cells andtissue usually remain responsive to endogenous serves and hormones inmost cases. In particular invention methods discussed below, localizedcoronary circulation provides targeted delivery to isolated regions ofthe heart. In some embodiments, proximity to endocardium allows accessby intracardiac injection. Therapeutic effects are often readilydetected eg., by use of standard electrophysiological assays as providedherein. Also importantly, many gene transfer-induced changes in accordwith the present invention can be rescued, if needed, by conventionalelectrophysiological methods.

Accordingly, and in one aspect the invention provides methods forpreventing or treating cardiac arrhythmia. More specific methods includeadministering to a mammal a therapeutically effective amount of at leastone polynucleotide that can increase or decrease at least one electricalproperty as determined by one or more standard electrophysiologicalassays. Examples of preferred administration routes, polynucleotides,and assays are provided in the discussion that follows. Preferably, theinvention further includes expressing the polynucleotide in the mammalsufficient to prevent or treat the cardiac arrhythmia. In general,polynucleotide expression conducive to using the invention is apparentas a shift in a recording (relative to baseline) obtained front at leastone of the standard electrophysiological assays.

In additionally preferred invention methods, the electrical property isincreased or decreased by at least about 10% relative to a baselinefunction. More preferably, the increase or decrease is at least about20%, more preferably at least about 30% to about 50% or more. Thatbaseline function can be readily ascertained eg., by performing theelectrophysiological assay on a particular mammal prior to conductingthe invention methods. Attentively, related baseline function can bedetermined by performing a parallel experiment in which a controlpolynucleotide is administered instead of the polynucleotide ofinterest. It will be apparent that once a reliable baseline function hasbeen established (or is available from public sources) determination ofthe baseline function by the practitioner may not always be necessary.Examples of relevant electrical properties are known and include, butare not limited to, at least one of refractoriness, speed of conduction,focal automaticity, and spatial excitation pattern.

The invention is widely applicable to the prevent and treatment of awide range of ventricular or atrial arrhythmias including atrialfibrillation. Accordingly, the invention provides, in one embodiment,methods for treating atrial fibrillation that include administering to amammal a therapeutically effective amount of at least one polynucleotideencoding an inhibitory G protein subunit, preferably Gα_(i2) subunit; ora functional fragment thereof. Preferred method practice involvesexpressing the polynucleotide in the mammal to treat the atrialfibrillation, particularly by controlling heart rate. Additionalprevention and treatment methods are provided below.

In another aspect, the invention provides a kit for performing one or acombination of the invention methods disclosed herein. Preferably, thekit includes at least one suitable myocardium nucleic acid deliverysystem and preferably at least one desired polynucleotide. Preferably,that polynucleotide is operably linked to the system i.e., it is infunctional and/or physical association therewith sufficient to providefor good administration of the polynucleotide into the heart.Additionally preferred kits include means for administering thepolynucleotide to the mammal such as a syringe, catheter and the like.

The invention also includes a device useful for the therapeutic methodsdisclosed herein. Preferred devices include those unitary, integraldevices elate position of the device within a subject, particularlyproximate to a patient's heart, as well as deliver a therapeutic agentto a patient, particularly a nucleic acid therapeutic to a mammalianheart. Specifically preferred devices comprise an elongate member,particularly a flexible catheter member that can be advanced to apatient's heart. The catheter unit suitably comprises a administrationmember, e.g. a needle member, for delivering a therapeutic agentespecially a polynucleotide to cardiac tissue of the patient. Thecatheter unit also includes positioning detection apparatus such asdetectable electrodes at the catheter's distal end.

Other invention embodiments are disclosed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B are photographs showing gene transfer to the AV node afterexposure to Adβgal. FIGS. 1C-D are photographs showing gene transfer tovarious non-target organ tissue.

FIG. 2A is a graph showing reduction in heart rate during atrialfibrillation after gene transfer of inhibitory G subunit (G_(i2)). FIG.2B is a related electrocardiogram.

FIG. 3A is a graph showing redaction in heart rate during atrialfibrillation after gene transfer of inhibitory G subunit (G_(i2)) andinfusion of epinephrine. FIG. 3B is a related electrocardiogram.

FIG. 4A is a Western blot of AV nodal tissue showing G_(i2)overexpression. FIG. 4B is a graph showing heart rate following genetransfer.

FIG. 5A is a graph showing comparison of I_(kr) in presence and absenceof gene transfer-mediated overexpression of HERG. FIG. 5B is aphotograph showing related action potential (AP).

FIG. 6 is a drawing showing changes in atrial action potential afterprolonged atrial fibrillation. The dotted tine indicates a normal atrialaction potential morphology.

FIG. 7A is a graph showing comparison of I_(kr) current in presence andabsence of gene transfer-mediated overexpression of dominant-negativemutant of HERG. FIG. 7B is a photograph showing related action potential(AP) of the mutant HERG.

FIGS. 8A and 8B depict a preferred therapeutic agent delivery device(intravascular injection catheter) of the invention. FIG. 8B shows theindicated area of device in expanded cross-section.

FIG. 9A is a drawing showing the amino acid sequence of the human G_(i2)sequence (NCBI protein sequence no. P04899).

FIGS. 9B-C are drawings showing the nucleic acid sequence encoding thehuman G_(i2) sequence shown in FIG. 9A. FIGS. 9B-C show the nucleic acidsequences in exon form.

FIGS. 10A-B are graphs showing actions potentials in guinea pigventricular myocytes expressing Kir2.1AAA.

DETAILED DESCRIPTION OF THE INVENTION

As discussed, the invention provides methods for the prevention ortreatment of cardiac arrhythmia in a subject mammal. By “treatment” ismeant use of the invention to reduce the severity of, prolong onset, oreliminate one or a combination of cardiac arrhythmias. Preferred methodsinvolve administering a therapeutically effective amount of at least onepolynucleotide capable of modulating at least one heart electricalproperty. More preferred methods involve expression of thepolynucleotide sufficient to prevent or treat the cardiac arrhythmia inthe mammal.

Preferred mammals include domesticated animals eg., pigs, horses, dogs,cats, sheep, goats and the like, rodents such as rats, hamsters andmice; rabbits; and primates such as monkeys, chimpanzees etc. A highlypreferred mammal is a human patient, preferably a patient who has or issuspected of having a cardiac arrhythmia. Methods of diagnosing andtreating a variety of cardiac arrhythmias have been disclosed. SeeCardiovascular Arrhythmias (1973) (Dreifus, L. S. and Likoff, W. eds)Grune & Stratton, NY; and references cited therein.

The invention is generally compatible with one or a combination ofsuitable polynucleotide administration routes including those intendedfor in vivo or ex vivo cardiac use. As discussed, there is understandingin the field that cardiac tissue is especially amenable to gene transfertechniques. See e.g, Donahue, J. et al. (1998) Gene Therapy 5: 630;Donahue, J. et al. PNAS (USA) 94: 4664(disclosing rapid and efficientgene transfer to the heart); Akhter, S. et al. (1997) PNAS (USA) 94:12100 (showing successful gene transfer to cardiac ventricularmyocytes); and references cited therein.

See also the Examples and Drawings provided herein which demonstrate,inter alia, successful use of myocardial gene transfer techniquesparticularly to address cardiac arrhythmia.

Typically preferred invention methods feature administration routes inwhich expression of the introduced polynucleotide directly or indirectlycauses a decrease in speed of conduction through at least one of: 1) theatrioventricular (AV) node (A-H interval) and 2) the His-Purkinjesystem. The decrease is readily detected and measured according toconventional means eg., by use of one or more of the standardelectrophysiological assays disclosed herein. Decreases of at leastabout 10% relative to baseline in the assay, preferably about 20% to 50%or more, are useful for many invention embodiments.

As will be appreciated, baseline values will often vary with respect tothe particular polynucleotides(s) chosen. Methods to quantify baselineexpression or protein include western blot, quantitative PCR, orfunctional assays such as adenylate cyclase assay for inhibitory Gproteins, patch clamp analysis for ion channel currents. EP effects canbe determined by measuring heart rate, conduction velocity or refractoryperiod in vivo with EP catheters.

Additionally preferred invention methods includes administration routesin which expression of the introduced polynucleotide directly orindirectly results in an increase in the AV node refractory period(AVNERP) as measured by the assay. An increase of at least about 10%relative to baseline in the assay, preferably at least about 20% toabout 50% or more, will be preferred in many invention embodiments.Conventional methods for detecting and measuring the AVNERP are knownand include the standard electrophysiological tests referenced herein.

Further preferred administration routes according to the inventioninvolve introducing the polynucleotide into cardiac tissue andexpressing same sufficient to detestably decrease heart rate asdetermined by a standard electrocardiogram (ECG) recording. Preferably,the decrease in heart rate is at least about 5% relative to baseline.Also preferably, the decrease in ventricular response rate or pulseduring the cardiac arrhythmia (eg., atrial fibrillation) is at leastabout 10% relative to baseline as determined by the recording.

As will be apparent, the invention is highly flexible and can be usedwith one or a combination of polynucleotides, preferably those encodingat least one therapeutic heart protein. A more preferredpolynucleotide: 1) either decreases the A-H interval or increases theAVNERP by at least about 10%, preferably at least about 20% to about50%, as determined by the electrophysiological assay; and 2) decreasesventricular response rate or pulse rate during atrial fibrillation by atleast about 10%, preferably at least about 20% to about 50% asdetermined by a standard electrocardiogram (ECG) recording.

Additionally preferred polynucleotides include, but are not limited to,those encoding at least one ion channel protein, gap junction protein, Gprotein subunit, connexin; or functional fragment thereof. Morepreferred are polynucleotides encoding a K channel subunit, Na channelsubunit, Ca channel subunit, an inhibitory G protein subunit; or afunctional fragment thereof. Additionally preferred polynucleotides willencode one, two or three of such proteins (the same or different).However polynucleotides encoding one of those proteins will be preferredfor most invention applications.

By the phrase “function fragment” is meant a portion of an amino acidsequence (or polynucleotide encoding that sequence) that has at leastabout 80%, preferably at least about 95% of the function of thecorresponding full-length amino acid sequence (or polynucleotideencoding that sequence). Methods of detecting and quantifyingfunctionality in such fragments are known and include the standardelectrophysiological assays disclosed herein.

For example, in embodiments in one or mom of the polynucleotides encodesan inhibitory G protein, a suitable test for assaying function of thatprotein (as well as functional fragments thereof) is the adenylatecyclase assay disclosed by Sugiyama A. et al. in J Cardiovasc Pharm1997; 29:734.

Suitable polynucleotides for practicing the invention can be obtainedfrom a variety of public sources including, but not limited to, GenBank(National Center for Biotechnology information (NCBI)), EMBL datalibrary, SWISS-PROT (University of Geneva, Switzerland), thePIR-International database; and the American Type Culture Collection(ATCC) (10801 University Boulevard, Manassas, Va. 20110-2209). Seegenerally Benson, D. A. et al. (1997) Nucl. Acids. Res. 25: 1 for adescription of Genbank.

More particular polynucleotides for use with the present invention arereadily obtained by accessing public information from GenBank. Forexample, in one approach, a desired polynucleotide sequence is obtainedfrom GenBank. The polynucleotide itself can be made by one or acombination of routine cloning procedures including those employingPCR-based amplification and cloning techniques. For example, preparationof oligonucleotide sequence, PCR amplification of appropriate libraries,preparation of plasmid DNA, DNA cleavage with restriction enzymes,ligation of DNA, introduction of DNA into a suitable host cell,culturing the cell, and isolation and purification of the closedpolynucleotide are known techniques. See eg., Sambrook et al. inMolecular Cloning: A Laboratory Manual (2d ed. 1989); and Ausubel et al.(1989), Current Protocols in Molecular Biology, John Wiley & Sons, NewYork.

Table 1 below, references illustrative polynucleotides from the GenBankdatabase for use with the present invention.

TABLE 1 Polynucleotide GenBank Accession No. Human Gi2 protein alphasubunit sequence: AH001470 Kir 2.1 potassium channel XM028411¹ HERGpotassium channel XM004743 Connexin 40 AF151979 Connexin 43 AF151980Connexin 45 U03493 Na channel alpha subunit NM000335 Na channel beta-1subunit NM001037 L-type Ca channel alpha-1 subunit AF201304 ¹Anadditional polynucleotide for use with the present invention is theKir2.1 AAA mutant, which is wild-type Kir 2.1 with a substitutionmutation of AAA for GFG in position 144-146.

Additional polynucleotides for use with the invention have been reportedin the following references: Wong et al. Nature 1991; 351(6321):63(constitutively active Gi2 alpha);) De Jongh K S, et al. J Biol Chem1990 Sep. 5; 265(25):14738 (Na and Ca channel beta subunits);Perez-Reyes, E. et al. J Biol Chem 1992 Jan. 25; 267(3):1792;Neuroscientist 2001 February; 7(1):42 (providing sodium channel beatsubunit information); Isom, L. L. Et al. Science 1992 May 8;256(5058):839 (providing the beta 1 subunit of a brain sodium channel);and Isom, L L. Et al. (1995) Cell 1995 Nov. 3; 83(3):433 (reporting beta2 subunit of brain sodium channels).

Further polynucleotides for use with the invention have been reported inPCT application number PCT/US98/23877 to Marban, E.

See also the following references authored by E. Marban: J. Gen Physiol.2001 August; 118(2):171-82; Circ. Res. 2001 Jul. 20; 89(2):160-7; CircRes. 2001 Jul. 20; 89(2):101; Circ Res. 2001 Jul. 6; 89(1):33-8; CircRes. 2001 Jun. 22; 88(12):1267-75; J Biol Chem. 2001 Aug. 10;276(32):30423-8; Circulation. 2001 May 22; 103(20):2447-52; Circulation.2001 May 15; 103(19):2361-4; Am J Physiol Heart Circ Physiol. 2001 June;280(6):H2623-30; Biochemistry. 2001 May 22; 40(20):6002-8; J Physiol.2001 May 15; 533(Pt 1):127-33; Proc Natl Acad Sci USA. 2001 Apr. 24;98(9):5335-40; Circ Res. 2001 Mar. 30; 88(6):570-7; Am J Physiol HeartCirc Physiol. 2001 April; 280(4):H1882-8; and J Mol Cell Cardiol. 2000November; 32(11):1923-30.

Further examples of suitable Ca channel subunits include beta 1, oralpha2-delta subunit from an L-type Ca channel. A preferred Na channelsubunit is beta1 or beta2. In some invention embodiments it will beuseful to select Na and Ca channel submits having having dominantnegative activity as determined by the standard electrophysiologicalassay described below. Preferably, that activity suppresses at leastabout 10% of the activity of the corresponding normal Na or Ca channelsubunit as determined in the assay.

Also preferred is the inhibitory G protein subunit (“Gα_(i2) ”) or afunctional fragment thereof.

The invention is broadly suited for use with gap junction proteins,especially those known or suspected, to be involved with cardiacfunction. Particular examples include connexin 40, 43, 45; as well asfunctional fragments thereof. Further contemplated are polynucleotidesthat encode a connexin having dominant negative activity as determinedby the assay, preferably a suppression activity of at least about 10%with respect to the corresponding normal connexin 40, 43, or 45.

Also envisioned are mutations of such polynucleotides that encodedominant negative proteins (muteins) that have detectable suppressoractivity. Encoded proteins that are genetically dominant typicallyinhibit function of other proteins particularly those proteins capableof forming binding complexes with the wild-type protein.

Additional polynucleotides of the invention encode, essentially but notentirely full-length protein. That is, the protein may not have all thecomponents of a full-length sequence. For example, the encoded proteinmay include a complete or nearly complete coding sequence (cds) but lacka complete signal or poly-adenylation sequence. It is preferred that apolynucleotide and particularly a cDNA encoding a protein of theinvention include at least a complete cds. That cds is preferablycapable of encoding a protein exhibiting a molecular weight of betweenabout 0.5 to 70, preferably between about 5 and 60, and more preferablyabout 15, 20, 25, 30, 35, 40 or 50 kB. That molecular weight can bereadily determined by suitable computer-assisted programs or by SDS-PAGEgel electrophoresis.

Although generally not preferred, the nucleic acid segment can be agenomic sequence or fragment thereof comprising one or more exonsequences. In this instance it is preferred that the cell, tissue ororgan selected for performing somatic cell gene transfer be capable ofcorrectly splicing any exon sequences so that a full-length or modifiedprotein can be expressed.

The polynucleotide and particularly the cDMA encoding the full-lengthprotein can be modified by conventional recombinant approaches tomodulate expression of that protein in the selected cells, tissues ororgans.

More specifically, suitable polynucleotides can be modified byrecombinant methods that can add, substitute or delete one or morecontiguous or non-contiguous amino acids from that encoded protein. Ingeneral, the type of modification conducted will relate to the result ofexpression desired.

For example, a cDNA polynucleotide encoding a protein of interest suchas an ion channel can be modified so as overexpress that proteinrelative to expression of the full-length protein (i.e. control assay).Typically, the modified protein will exhibit at least 10 percent orgreater overexpression relative to the full-length protein; morepreferably at least 20 percent or greater; and still more preferably atleast about 30, 40, 50, 60, 70, 80, 100, 150, or 200 percent or greateroverexpression relative to the control assay.

As noted above, further contemplated modifications to a polynucleotide(nucleic acid segment) and particularly a cDNA are those which createdominant negative proteins.

In general, a variety of dominant negative proteins can be made bymethods known in the field. For example, ion channel proteins arerecognized as one protein family for which dominant negative proteinscan the readily made, e.g., by removing selected transmembrane domains.In most cases, the function of the ion channel binding complex issubstantially reduced or eliminated by interaction of a dominantnegative ion channel protein.

Several specific strategies have been developed to make dominantnegative proteins. Exemplary of such strategies include oligonucleotidedirected and targeted deletion of cDNA sequence encoding the desiredprotein. Less preferred methods include nucleolytic digestion orchemical mutagenesis of the cDNA.

It is stressed that creation of a dominant negative protein is notsynonymous with other conventional methods of gene manipulation such asgene deletion and antisense RNA. What is meant by “dominant negative” isspecifically what is sometimes referred to as a “poison pill” which canbe driven (i.e. expressed) by an appropriate DNA construct to produce adominant negative protein which has capacity to inactivate an endogenousprotein.

For example, in one approach, a cDNA encoding a protein comprising oneor more transmembrane domains is modified so that at least 1 andpreferably 2, 3, 4, 5, or more of the transmembrane domains areeliminated. Preferably, the resulting modified protein forms a bindingcomplex wife at least one other protein and usually more than one otherprotein. As noted, the modified protein will inhibit normal function ofthe binding complex as assayed, e.g., by standard ligand binding assaysor electrophysiological assays as described herein. Exemplary bindingcomplexes are those which participate in electrical charge propagationsuch as those occurring in ion channel protein complexes. Typically, adominant negative protein will exhibit at least 10 percent or greaterinhibition of the activity of the binding complex; more preferably atleast 20 percent or greater; and still more preferably at least about30, 40, 50, 60, 70, 80, or 100 percent or greater inhibition of thebinding complex activity relative to the full-length protein.

As a further illustration, a cDNA encoding a desired protein for use inthe present methods can be modified so that at least one amino acid ofthe protein is deleted. The deleted amino acid(s) can be contiguous ornon-contiguous deletions essentially up to about 1%, more preferablyabout 5%, and even more preferably about 10, 20, 30, 40, 50, 60, 70, 80,or 95% of the length of the full-length protein sequence.

Alternatively, the cDNA encoding the desired protein can be modified sothat at least one amino acid in the encoded protein is substituted by aconservative or non-conservative amino acid. For example, a tyrosineamino acid substituted with a phenylalanine would be an example of aconservative amino acid substitution, whereas an arginine replaced withan alanine would represent a non-conservative amino acid substitution.The substituted amino acids can be contiguous or non-contiguoussubstitutions essentially up to about 1%, more preferably about 5%, andeven more preferably about 10, 20, 30, 40, 50, 60, 70, 80, or 95% of thelength of the full-length protein sequence.

Although generally less-preferred, the nucleic acid segment encoding thedesired protein can be modified so that at least one amino acid is addedto the encoded protein. Preferably, an amino acid addition does notchange the ORF of the eds. Typically, about 1 to 50 amino adds will beadded to the encoded protein, preferably about 1 to 25 amino acids, andmore preferably about 2 to 10 amino acids. Particularly preferredaddition sites ate at the C- or N-terminus of the selected protein.

Preferred invention practice involves administering at least one of theforegoing polynucleotides with a suitable myocardium nucleic aciddelivery system. In one embodiment, that system includes a non-viralvector operably linked to the polynucleotide. Examples of such non-viralvectors include the polynucleoside alone or in combination with asuitable protein, polysaccharide or lipid formulation.

Additionally suitable myocardium nucleic acid delivery systems includeviral vector, typically sequence from at least one of an adenovirus,adenovirus-associated virus (AAV), helper-dependent adenovirus,retrovirus, or hemagglutinating virus of Japan-liposome (HVJ) complex.Preferably, the viral vector comprises a strong eukatyotic promoteroperably linked to the polynucleotide eg., a cytomeglovirus (CMV)promoter.

Additionally preferred vectors include viral, vectors, fusion proteinsand chemical conjugates. Retroviral vectors include moloney murineleukemia viruses and HIV-based viruses. One preferred HIV-based viralvector comprises at least two vectors wherein the gag and pol genes arefrom an HIV genome and the env gene is from another virus. DNA viralvectors are preferred. These vectors include pox vectors such asorthopox or avipox vectors, herpesvirus vectors such as a herpes simplexI virus (HSV) vector [Geller, A. I. et al., J. Neurochem, 64; 487(1995); Lim, F., et al., in DNA Cloning: Mammalian Systems, D. Glover,Ed. (Oxford Univ. Press, Oxford England) (1995); Geller, A. I., et al.,Proc Natl. Acad. Sci.: U.S.A.: 90 7603 (1993); Geller, A. I., et al.,Proc Natl. Acad. Sci USA: 87:1149 (1990)]; Adenovirus Vectors [LeGalLaSalle et al., Science, 259:988 (1993); Davidson, et al., Nat. Genet 3:219(1993); Yang, et al., J. Virol. 69: 2004 (1995)] and Adeno-associatedVirus Vectors [Kaplitt, M. G., et al., Nat. Genet. 8:148 (1994)].

Pox viral vectors introduce the gene into the cells cytoplasm. Avipoxvirus vectors result in only a short term expression of the nucleicacid. Adenovirus vectors, adeno-associated virus vectors and herpessimplex virus (HSV) vectors are may be indication for some inventionembodiments. The adenovirus vector results in a shorter term expression(eg., less than about a month) than adeno-associated virus, in someembodiments, may exhibit much longer expression. The particular vectorchosen will depend upon the target cell and the condition being treated.Preferred in vivo or ex vivo cardiac administration techniques havealready been described.

To simplify the manipulation and handling of the polynucleotidesdescribed herein, the nucleic acid is preferably inserted into acassette where it is operably linked to a promoter. The promoter must becapable of driving expression of the protein in cells of the desiredtarget tissue. The selection of appropriate promoters can readily beaccomplished. Preferably, one would use a high expression promoter. Anexample of a suitable promoter is the 763-base-pair cytomegalovirus(CMV) promoter. The Rous sarcoma virus (RSV) (Davis, et al., Hum GeneTher 4:151 (1993)) and MMT promoters may also be used. Certain proteinscan expressed using their native promoter. Other elements that canenhance expression can also be included such as an enhancer or a systemthat results in high levels of expression such as tat gene and tarelement. This cassette can then be inserted into a vector, e.g., aplasmid vector such as pUC118, pBR322, or other known plasmid vectors,that includes, for example, an E. coli origin of replication. See,Sambrook, et al., Molecular Cloning: A Laboratory Manual, Cold SpringHarbor Laboratory press, (1989). The plasmid vector may also include aselectable marker such as the β-lactamase gene for ampiclllinresistance, provided that the marker polypeptide does not adverselyeffect the metabolism of the organism being heated. The cassette canalso be bound to a nucleic acid binding moiety in a synthetic deliverysystem, such as the system disclosed in WO 95/22618.

If desired, the polynucleotides of the invention may also be used with amicrodelivery vehicle such as cationic liposomes and adenoviral vectors.For a review of the procedures for liposome preparation, targeting anddelivery of contents, see Mannino and Gould-Fogerite, BioTechniques,6:682 (1988). See also, Felgner and Holm, Bethesda Res. Lab. Focus,11(2):21 (1989) and Maurer, R. A., Bethesda Res. Lab. Focus, 11(2):25(1989).

Replication-defective recombinant adenoviral vectors, can the producedin accordance with known techniques. See, Quantin, et al., Proc. Natl.Acad. Sci. USA 89:2581-2584 (1992); Stratford-Perricadet, et al., J.Clin. Invest., 90:626-630 (1992); and Rosenfeld, et al., Cell,68:143-155 (1992).

The effective dose of the nucleic acid will be a function of theparticular expressed protein, the particular cardiac arrhythmia to betargeted, the patient and his or her clinical condition, weight, age,sex, etc.

One preferred myocardium delivery system is a recombinant viral vectorthat incorporates one or more of the polynucleotides therein, preferablyabout one polynucleotide. Preferably, the viral vector used in theinvention methods has a pfu (plague forming units) of from about 10⁸ toabout 5×10¹⁰ pfu. In embodiments in which the polynucleotide is to beadministered with a non-viral vector, use of between from about 0.1nanograms to about 4000 micrograms will often be useful eg., about 1nanogram to about 100 micrograms.

Choice of a particular myocardium delivery system will be guided byrecognized parameters including the cardiac arrhythmia of interest andthe amount and length of expression desired. Use of virus vectorsapproved for human applications eg., adenovirus are particularlypreferred.

As discussed, it is an object of the invention to prevent or treatcardiac arrhythmia. In one embodiment the method further includesoverexpressing a potassium (K) channel protein subunit sufficient todecrease cardiac action potential duration (APD) by at least about 5% asdetermined by the standard cardiac electrophysiological assay.

Reference herein to an electrophysiological assay is meant aconventional test for determining cardiac action potential (AP). Seegenerally Fogoros R N. Electrophysiologic Testing Blackwell Science,Inc. (1999.) for disclosure relating to performing such tests.

Specific reference herein to a “standard electrophysiological assay” ismeant the following general assay.

1) providing a mammalian heart (in vivo or ex vivo)

2) contacting the heart with at least one suitable polynucleotidepreferably in combination with an appropriate myocardium nucleic aciddelivery system,

3) transferring the polynucleotide into cells of the heart underconditions which allow expression of the encoded amino acid sequence;and

4) detecting modulation (increase or decrease) of at least oneelectrical property in the transformed heart eg., at least one ofconduction, ventricular response rate, and pulse rate.

Particular invention methods include modifying the polynucleotide alonglines discussed above sufficient to overexpress the encoded protein.Further preferred are methods in which the nucleic acid is modified toproduce a dominant negative ion channel protein. The ion channel proteincan be e.g., a sodium, calcium, voltage-gated, or ligand-gated ionchannel sad particularly a potassium ion channel. Additional disclosurerelating to such channel proteins can be found in the discussion aboveand in U.S. Pat. No. 5,436,128, for instance.

Practice of the invention is broadly compatible with one or acombination of different administration (delivery) systems.

In particular, one suitable administration route involves one or moreappropriate polynucleotide into myocardium. Alternatively, on inaddition, the administration step includes perfusing the polynucleotideinto cardiac vasculature. If desired, the administration step canfurther include increasing microvascular permeability using routineprocedures, typically administering at least one vascular permeabilityagent prior to or during administration of the gene transfer vector.Examples of particular vascular permeability agents includeadministration of one or more of the following agents preferably itscombination with a solution having less than about 500 micromolarcalcium: substance P, histamine, acetylcholine, an adenosine nucleotide,arachidonic acid, bradykinin, endothelin, endotoxin, interleukin-2,nitroglycerin, nitric oxide, nitroprusside, a leukotriene, an oxygenradical, phospholipase, platelet activating factor, protamine,serotonin, tumor necrosis factor, vascular endothelial growth factor, avenom, a vasoactive amine, or a nitric oxide synthase inhibitor. Aparticular is serotonin, vascular endothelial growth factor (VEGF), or afunctional VEGF fragment to increase the permeability.

Typical perfusion protocols in accord with the invention are generallysufficient to transfer the polynucleotide to at least about 10% ofcardiac myocytes in the mammal. Infusion volumes of between from about0.5 to about 500 ml are preferred. Also preferred are coronary flowrates of between from about 0.5 to about 500 ml/min. Additionallypreferred perfusion protocols involve the AV nodal artery. Transformedheart cells, typically cardiac myocytes that include the polynucleotideare suitably positioned at or near the AV node.

Illustrative strategies for detecting modulation of transformed hearthave been disclosed eg., in Fogoros R N, supra. A preferred detectionstrategy is performing a conventional electrocardiogram (ECG).Modulation of cardiac electrical properties by use of the invention isreadily observed by inspection of the ECG. See also the Examples andDrawings below.

More specific methods for preventing or treating cardiac arrhythmiainclude overexpressing a K channel protein sub-unit sufficient todecrease surface electrocardiogram (ECG) repolarization time by at leastabout 5%, preferably at least about 10% to about 20%, as determined bythe assay. Typically, the K channel protein subunit is overexpressed byat least about 2 fold, preferably about 5 fold, relative to anendogenous K channel protein as determined by a standard Northern orWestern blot assay. Also preferably, the K channel protein subunit isoverexpressed and impacts repolarization in congestive heart failure ormyocardial infarction in the long QT syndrome.

In particular embodiments, methods for preventing or treating cardiacarrhythmia provided herein further include decreasing conduction throughcardiac tissues by at least about 5%, preferably at least about 10% toabout 20%, as determined by the standard electrophysiological assay.

As discussed, the invention is one of general application that can beused one or a combination of different cardiac arrhythmias. Examples ofparticular arrhythmias has been disclosed by Bigger, J. T and B. F.Hoffman, supra. More specific examples include atrial flutter, atrialfibrillation, and ventricular tachycardia. Other examples include sinusbradycardia, sinus tachycardia, atrial tachycardia, atrial fibrillation,atrial flutter, atrioventricular nodal block, atrioventricular nodereentry tachycardia, atrioventricular reciprocating tachycardia,ventricular tachycardia or ventricular fibrillation.

The following sections 1-5 discuss particular uses of the presentinvention.

1. Sinus Bradycardia: Direct injection or intravascular perfusion ofmaterials/vectors into the atria or ventricles in order to create adiscrete focus of electrically active tissue to replace the function ofthe sinus node. Indications might include: sick sinus syndrome,Stokes-Adams attacks, syncope, chronic fatigue syndrome,cardiomyopathies (hypertrophic and dilated), and all other present andfuture indications for electronic pacemakers. Therapeutic genes couldinclude wild-type or mutated potassium, HCN and/or calcium channelsubunits to increase local automaticity and/or to induce pacemakeractivity where it is not normally present.

2. Inappropriate Sinus Tachycardia: Modification of the automaticity inthe sinus node and/or surrounding atrial tissue for the treatment ofinappropriate sinus tachycardia, e.g. by introducing K channel, Cachannel or HCN channel genes to decrease nodal excitability

3. Atrial Fibrillation/Atrial Flutter/Atrial Tachycardia: Directinjection or intravascular perfusion of materials/vectors in order to:(1) produce lines of conduction block in order to prevent conduction ofreentry-type atrial arrhythmias, (2) suppress automaticity or increaserefractoriness in order to ablate discrete arrhythmic foci of tissue,(3) affect conduction velocity, refractoriness or automaticity diffuselythroughout the atria in order to prevent or treat atrial fibrillation,multifocal atrial tachycardia or other atrial tachycardias with multipleor diffuse mechanisms, or (4) Direct injection into the atrioventricularnode or perfusion of the atrioventricular nodal artery withmaterials/vectors to after the conduction properties (conductionvelocity, automaticity, refractoriness) of the atrioventricular node inorder to slow the ventricular response rate to atrial arrhythmias.

4. Atrioventricular nodal block: Direct injection or intracoronaryperfusion of materials/vectors into the atrioventricular nodal region orinto the ventricles in order to (1) create a discrete focus ofelectrically active tissue to initiate the heart beat in the absence ofatrioventricular nodal conduction of the normal impulse from the atria,or (2) reestablish function of the atrioventricular node.

5. Ventricular Tachycardia/Ventricular Fibrillation: Delivery of vectorsby: (1) Direct injection into discrete foci of ventricular myocardium tosuppress automaticity or increase refractoriness in order to ablatearrhythmic foci by genetic means, (2) Diffuse direct injection orcoronary artery perfusion of materials/vectors into both ventricles toaffect the conduction properties (conduction velocity, automaticity,refractoriness) of ventricular tissue in order to treat or preventventricular arrhythmias, or (3) Direct injection of materials/vectors toproduce lines of conduction block in order to prevent conduction ofreentry-type ventricular arrhythmias.

As also discussed, the present invention provides more specific methodsfor preventing or treating ventricular rate or pulse during atrialfibrillation. In one embodiment, the method includes administering tothe mammal a therapeutically effective amount of at least onepolynucleotide encoding a Gα_(i2) subunit or a functional fragmentthereof. Typically preferred methods further include expressing thepolynucleotide in the mammal to prevent or treat the atrialfibrillation. Preferred methods also include overexpressing the Gα_(i2)subunit or a functional fragment thereof sufficient to decrease speed ofconduction through the atrioventricular (AV) node (A-H interval) orHis-Purkinje system as determined by a standard electrophysiologicalassay. Also preferably, the decrease in the A-H interval is accompaniedby an increase in AV node refractory period (AVNERP). The decrease inthe A-H interval is at least about 10%, preferably at least about 20%,as determined by the assay. The increase in AVNERP is at least about10%, preferably at least about 20%, as determined by the assay.

By the phrase “therapeutically effective” amount or related phrase is anamount of administered polynucleotide needed to achieve a desiredclinical outcome.

In one embodiment of the foregoing specific method, overexpression ofthe Gα_(i2) or a functional fragment thereof is capable of decreasingpulse rate or ventricular rate during atrial fibrillation as determinedby a standard cardiac electrophysiological assay. Preferably, thedecrease in pulse rate or ventricular rate during atrial fibrillation isat least about 10%, preferably at least about 20%, as determined by theassay.

The foregoing embodiment of the invention for preventing or treatingatrial fibrillation provides specific advantages. For example, it hasbeen found that it is possible to transfer genes to half of AV nodalcells with clinically relevant delivery parameters. Desirabletherapeutic effects of the gene therapy include slewing of AV nodalconduction and increases of the refractory period of the AV node, withresultant slowing of the ventricular response rate during atrialfibrillation. The work provides proof of principle that gene therapy isa viable option for the treatment of common arrhythmias.

In one invention embodiment, the polynucleotide encoding the Gα_(i2)subunit hybridizes to the nucleic acid sequence shown in FIGS. 9B-C (SEQID NO. 1); or the complement thereof under high stringency hybridizationconditions. Encoded amino acid sequence is shown in FIG. 9A (SEQ ID NO.2). By the phrase “high stringency” hybridization conditions is meantnucleic acid incubation conditions approximately 65° C. in 0.1×SSC. SeeSambrook, et al., infra. Preferably, the polynucleotide consists of orcomprises the nucleic acid shown in FIGS. 9B-C (SEQ ID NO. 1). FIGS.9A-C show the subunit nucleotide sequence as exon representations. Itwill be appreciated that in the gene sequence, the exons are covalentlylinked together end-to-end (exon 1, 2, etc)

As discussed, it is an object of the present invention to use genetherapy as an antiarrhythmic strategy. The Examples section, inparticular, focuses genetic modification of the AV node. Anintracoronary perfusion model for gene delivery, building on previouswork in isolated cardiac myocytes and ex vivo-perfused hearts has beendeveloped.^(4,5). Using this method, porcine hearts were infected withAdβgal (a recombinant adenovirus expressing E. coli β-galactosidase) orwith AdG_(i) (encoding the Gα_(i2) subunit). Gα_(i2) expressionsuppressed baseline AV conduction and slowed the heart rate duringatrial fibrillation, without producing complete heart block. Incontrast, expression of the reporter gene β-galactosidase had noelectrophysiological effects. These results demonstrate the feasibilityof using myocardial gene transfer strategies to treat commonarrhythmias.

More generally, the invention can be used to deliver and express adesired ion channel, extracellular receptor, or intracellular signalingprotein gene in selected cardiac tissues, particularly to modify theelectrical properties of that tissue, e.g., increasing or decreasing itsrefractoriness, increasing or decreasing the speed of conduction,increasing or decreasing focal automaticity, and/or altering the spatialpattern of excitation. The general method involves delivery of geneticmaterials (DNA, RNA) by injection of the myocardium or perfusion throughthe vasculature (arteries, veins) or delivery by nearly any othermaterial sufficient to facilitate transformation into the targetedportion of the myocardium using viral (adenovirus, AAV, retrovirus, HVJ,other recombinant viruses) or non-viral vectors (plasmid, liposomes,protein-DNA combinations, lipid-DNA or lipid-virus combinations, othernon-viral vectors) to treat cardiac arrhythmias.

By way of illustration, genes that could be used to affect arrhythmiasinclude ion channels and pumps (α subunits or accessory subunits of thefollowing: potassium channels, sodium channels, calcium channels,chloride channels, stretch-activated cation channels, HCN channels,sodium-calcium exchanger, sodium-hydrogen exchanger, sodium-potassiumATPase, sarcoplasmic reticular calcium ATPase), cellular receptors andintracellular signaling pathways (α or β-adrenergic receptors,cholinergic receptors, adenosine receptors, inhibitory G protein αsubunits, stimulatory G protein α subunits, Gβγ subunits) or genes forproteins that affect the expression, processing or function processingof these proteins.

Selection of the appropriate gene(s) for therapy can be performed byanyone with an elementary knowledge of cardiac electrophysiology. Inaddition, the effects of ion channel expression can be simulated bycomputer programs to anticipate the effects of gene transfer. Thedelivery methods for myocardial delivery are widely reported, andmethods involving injection of the myocardium or intravascular perfusionhave been used successfully.

More specific advantages of the invention include ability to conveylocalized effects (by focal targeted gene delivery), reversible effects(by use of inducible vectors, including those already reported as wellas new generations of such vectors, including but not limited toadeno-associated vectors using tetracycline-inducible promoters toexpress wild-type or mutant ion channel genes), gradedness (by use ofinducible vectors as noted above, in which gradedness would the achievedby titration of the dosage of the inducing agent), specificity oftherapy based on the identity of the gene construct, ability to regulatetherapeutic action by endogenous mechanisms (nerves or hormones) basedon the identity of the gene construct, and avoidance of implantablehardware including electronic pacemakers and AICDs, along with theassociated expense and morbidity.

As discussed above, the invention also includes devices useful in thetreatment methods of the invention. These devices include catheters thatinclude in a single unitary unit that contain both delivery and positiondetection features. FIGS. 8A and 8B show catheter unit 10 that containsat proximal end 12 (i.e. end manipulated by medical practitioner,typically external to patient) electrical connection 14, therapeuticagent injection port and needle extension mechanism 16, and steeringcontrol 18. Distal end 20 of catheter 10 includes electrodes 22 fordetection of the distal end position within a patient and retractable 24for delivery of the therapeutic agent, particularly a polynucleotide totargeted tissue, especially a polynucleotide to mammalian cardiactissue. The needle 24 can be manipulated by extension mechanism 16.Connection 14 enables activation of detection apparatus 22. Atherapeutic agent such as a polynucleotide can be injected or otherwiseintroduced into device 10 via injection port 16. FIG. 8B shows thespecified catheter region in cross-section with electrode cables 30 thatprovide communication between electrical connection 14 and electrodes22, steering rod 32 that can enable manipulation of catheter 10 withinthe patient via steering control 14, and injector connection or tubing34 that provides a path for delivery of the therapeutic agent throughcatheter 10 to the targeted tissue of the patient. The device issuitably employed in a minimally invasive (endoscopic) procedure.

Variations of the depicted design also will be suitable. For instance,the catheter may comprise a tip (distal portion) with a fixed curve.Additionally, rather than having the therapeutic agent traverse thecatheter 10, the agent may be housed within a reservoir, which may beactivated (i.e. therapeutic agent released to patient) via mechanism atcatheter proximal end. The needle 24 may be a straight needle or ascrew-type apparatus. In each design, the device suitable contains sometype of detection apparatus, e.g. electrodes that provide forelectrophysiologically-guided substance injections into the targetedtissue.

The following specific examples are illustrative of the invention.

EXAMPLE 1 Gene Transfer of β-Galactosidase (β-Gal) and Inhibitory GProtein Subunit (Gα_(i2)) into Cardiac Tissue

In previous in vivo and in vitro studies, we found that gene transferefficiency correlated with coronary flow rate, virus exposure time,virus concentration, and the level of microvascular permeability^(4,5).We also found that elimination of radiographic contrast media and redblood cells from the perfusate and delivery at body temperature werenecessary for optimal results. The in vivo delivery system used in thisreport builds on those findings.

Ten animals underwent a protocol that included medication with oralsildenafil before baseline electrophysiology (EP) study, catheterizationof the right coronary artery, and infusion of VEGF, nitroglycerin andvirus-containing solutions (7.5×10⁹ pfu in 1 ml) into the AV nodalbranch of the right coronary artery. VBGF was used to increasemicrovascular permeability⁶, and sildenafil potentiated the VEGF effect.The infusion volume and coronary flow rate were limited to avoid effluxfrom the artery and infection of outer regions of the heart. Fiveanimals received Adβgal, and the other 5 received AdG_(i). The animalsunderwent follow-up EP study 7 days after virus infusion. After thesecond EP study, the hearts were explanted and evaluated forβ-galactosidase (β-gal) and Gα_(i2) expression. Other adenoviral genetransfer studies have shown that expression is detectable after 3 days,peaks after 5-7 days, and then regresses over 20-30 days⁷⁻⁹. Based onthese data, we tested for gene expression and phenotypic changes 7 daysafter gene delivery.

X-gal staining revealed β-gal activity in the AV nodal region andadjacent ventricular septum of all Adβgal-infected animals (FIG. 1 a).There was no evidence of β-gal activity in any of the AdG_(i)-infectedanimals or in other heart sections from the Adβgal group. Microscopicsections through the AV node documented gene transfer to 45±16% of theAV nodal cells in the Adβgal group and confirmed the absence of X-galstaining in the AdG_(i)-infected animals. Also notable in themicroscopic sections was a mild inflammatory infiltrate, comprisedmainly of mononuclear cells.

Western blot analysis was performed on tissue homogenates from the AVnodal region of 4 animals from each group (FIG. 1 b). Densitometryanalysis confirmed Gα_(i2) overexpression in the AdG_(i) group,amounting to a 5-fold increase in Gα_(i2) relative to the Adβgal animals(p=0.01). The level of Gα_(i2) in the Adβgal group was not differentfrom that found in 2 uninfected control animals.

X-gal staining of gross and microscopic sections from the lung, liver,kidney, skeletal muscle and ovaries of all animals was performed toevaluate the extent of gene transfer outside the heart (FIG. 1 c). Inthe Adβgal-infected animals, β-gal activity was evident in grossspecimens from the liver, kidneys and ovaries, but not in the lungs orskeletal muscle. Microscopic sections revealed definite β-gal activity,but in less than 1% of the cells in these organs. X-gal staining was notfound in any tissues of the AdG_(i)-infected or uninfected controlanimals. The lack of X-gal staining in AdG_(i)-infected and uninfectedcontrols indicates that the results were specific for transgeneexpression and not from endogenous β-gal activity or false-positivestaining. These results are consistent with a previous study documentinggene expression in peripheral organs after intracardiac injection ofadenovirus¹⁰, and suggest that ongoing clinical gene therapy trialsshould consider the risks of non-target organ gene transfer.

FIGS. 1A-D are explained in more detail as follows. Measurement of genetransfer efficacy. FIG. 1A. X-gal staining of a transverse sectionthrough the AV groove. Arrowheads indicate the tricuspid valve ring, andthe solid arrow marks the central fibrous body. The hollow arrow pointsto the AV node. FIG. 1B. A microscopic section through the AV node showsgene transfer to 45±6% of myocytes. Cells expressing β-galactosidase arestained blue. FIG. 1C. Gross and microscopic pathology after exposure ofliver, kidney and ovary to X-gal solution. FIG. 1D. Microscopic sectionsshow rare blue cells in these organs (arrowheads). Lung and skeletalmuscle failed to show any evidence of gene transfer.

EXAMPLE 2 Electrophysiological Analysis of Cardiac Tissue Transducedwith β-Gal or Inhibitory G Protein (Gα_(i2)) Subunit

Electrophysiological measurements obtained at baseline and 7 days afterinfection are displayed in Table 2, below.

TABLE 2 Electrophysiological Parameters Before and 7 Days After GeneTransfer Adβgal AdG_(i) Day 0 7 0 7 Heart rate during sinus 114 ± 5 111± 1  113 ± 2  106 ± 4  rhythm ECG: P-R Interval 101 ± 1 99 ± 1 97 ± 2109 ± 5* QRS interval  58 ± 2 54 ± 1 57 ± 1 56 ± 1 Q-T interval 296 ± 6310 ± 2  288 ± 7  316 ± 6  A-H interval  61 ± 1 61 ± 1 60 ± 2  76 ± 3*H-V Interval  23 ± 1 25 ± 1 23 ± 1 24 ± 1 AVNERP 226 ± 6 224 ± 4  226 ±6  246 ± 3* mean ± s.e.m., n = 5 in each group, *p ≦ 0.03; AVNERP: AVnode effective refractory period

ECG parameters were taken from the surface ECG, and the A-H and H-Vintervals were recorded from an intracardiac-catheter in the His-bundleposition. (The A-H internal measures conduction time through the AVnode, and the H-V interval is the conduction time through theHis-Purkinje system.) The AV node effective refractory period (AVNERP)was measured by pacing the atria at a stable rate for 8 beats and thendelivering premature atrial stimuli at progressively shorter intervals,noting the interval where the premature beat failed to conduct throughthe AV node. There were no significant differences in theelectrophysiological parameters between groups at baseline. In theAdβgal group, comparison of baseline measurements to those taken 7 daysafter infection also failed to show any significant differences. Incontrast, the follow-up study of the AdG_(i) revealed significantprolongation in the P-R interval on the surface ECG (paired analysis,day 0: 97±2 msec, day 7: 109±4 msec, p=0.01), the A-H interval on theintracardiac electrogram (day 0: 60±2 msec, day 7: 76±3 msec, p=0.01)and the AVNBRP (day 0: 226±6 msec, day 7: 246±3 msec, p=0.03),indicating both slowed conduction and increased refractoriness of the AVnode after Gα_(i2) overexpression.

EXAMPLE 3 Measurement of Heart Rate to Cardiac Tissue Transduced withβ-Gal or Inhibitory G Protein (Gα_(i2)) Subunit

After measurement of basic electrophysiological intervals, we measuredthe heart rate during acute episodes of atrial fibrillation.Overexpression of Gα_(i2) in the AV node caused a 20% reduction in theventricular rate during atrial fibrillation (day 0: 199±5 bpm, day 7:158±2 bpm, p=0.005). This effect persisted in the setting of adrenergicstimulation. Administration of epinephrine (1 mg, IV) increased theatrial fibrillation heart rate in all animals, but the groupoverexpressing Gα_(i2), nevertheless, exhibited a 16% reduction inventricular rate (day 0: 364±3 bpm, day 7: 308±2 bpm, p=0.005). Incontrast, β-gal expression did not affect the heart rate during atrialfibrillation, either before (day 0: 194±8 bpm, day 7: 193±7 bpm, p=NS)or after epinephrine administration (day 0: 362±6 bpm, day 7: 353±5,p=NS).

To further evaluate the effect of Gα_(i2) overexpression on AVconduction, we analyzed the heart rate at various time points afterinduction of atrial fibrillation in the AdG_(i)-epinephrine group. Thesedata indicate that the ventricular rate remains stable and that thebeneficial suppression of heart rate from Gα_(i2) gene transfer issustained through at least 3 minutes of observation. The episodes ofatrial fibrillation often lasted longer than 3 minutes (see methods),but the period of observation was limited to ensure that the effects ofepinephrine would be constant.

The choice of Gα_(i2) to suppress conduction was inspired by the successof β-blocking drugs at achieving that goal. In the AV node, β-adrenergicreceptors are coupled to stimulatory G proteins (G_(s)). Stimulation ofβ-receptors activates G_(s), releasing the Gα_(s)-subunit to stimulateadenylate cyclase¹¹. This process leads to a cascade of intracellularevents causing an increase in conduction velocity and a shortening ofthe refractory period. β-blockers prevent the increase in AV nodalconduction by inhibiting receptor activation.

The intracellular processes responsive to G_(s) are counterbalanced bythe activity of inhibitory G proteins (G_(i)). In the AV node, G_(i) arecoupled to muscarinic M2 and adenosine A1 receptors¹¹. G_(i) activationreleases the G_(α) _(i)-subunit to bind and inhibit adenylate cyclaseactivity and the Gβγ-subunit to increase potassium conductance by directaction on acetylcholine-activated potassium channels. The cumulativeeffect of G_(i) activation is a decrease in conduction through the AVnode. In agreement with these known effects of the G protein cascade,our data show that overexpression of Gα_(i2) suppresses AV nodalconduction in the drug-free state and during adrenergic stimulation.

Under ordinary circumstances, Gα_(i2)-mediated inhibition of adenylatecyclase requires receptor activation¹². In the current study, however,Q_(i) activity appears to be uncoupled from the receptor, since theinhibition occurs without exogenous M2 or A1 receptor stimulation. Inthe setting of 5-fold overexpression of Gα_(i2), normal cellularmechanisms may well be altered. Further study will be required toelucidate the changes in signal transduction that underlie the observedeffects.

A principal focus of this study was to overcome the problem of vectordelivery to the myocardium using minimally invasive techniques. Bymanipulation of the tissue and vascular dynamics, the β-galactosidaseand Gα_(i2) genes were transferred to 45% of AV nodal myocytes byintracoronary catheterization. A limited inflammatory response was notedafter adenoviral infection, but there was no detectable effect on AVnodal function from the inflammation or from reporter gene transfer.Other studies have shown that the use of first-generation adenoviruses(those with E1 deletions) leads to intense inflammation and loss oftransgene expression 20-30 days after infection¹³. When used at highconcentrations (much greater than those in this study), adenovirusvectors are also associated with endothelial damage, arterialthrombosis, thrombocytopenia, anemia, hepatitis, and death¹⁴⁻¹⁷.Wild-type adenoviruses have also been implicated in the development ofmyocarditis and idiopathic cardiomyopathy¹⁸. Since this study used arelatively low concentration of virus and looked at phenotypic changesearly after gene transfer, these limitations did not affect the findingsreported here.

This study is the first report of intracoronary site-specific genetransfer, as well as the first use of gene therapy to treat cardiacarrhythmias. We demonstrate that overexpression of an inhibitorycomponent of the β-adrenergic signaling pathway suppresses AV nodalconduction, and also document the absence of electrophysiologicalchanges after adenovirus-mediated transfer of a reporter gene. Insummary, our research provides proof of the principle that in in vivogene transfer can modify the cardiac electrical substrate and lays thegroundwork for future investigations to treat common arrhythmias.

FIGS. 2A-B and 3A-B are explained in more detail as follows. Reductionin heart rate during atrial fibrillation after Gα_(i2) gene transfer. Inthe drug-free state, Gα_(i2) overexpression reduces ventricular rate by20% during atrial fibrillation. No difference in heart rate is observedafter Adβgal exposure. After infusion of epinephrine (1 mg, IV), therelative effect of Gα_(i2) overexpression persists (

p=0.005).

EXAMPLE 4 Heart Rate Control during Atrial Fibrillation

Use present example shows conduction slowing and increasedrefractoriness.

Atrial fibrillation affects more than 2 million people in the UnitedStates, including 5-10% of people over the age of 65 and 10-35% of the 5million patients with congestive heart failure. Treatment strategies forAF include antiarrhythmic therapy to maintain sinus rhythm orventricular rate control and anticoagulation. Although appealing, themaintenance of sinus rhythm is often unsuccessful. Within 1 year ofconversion to sinus rhythm, 25-50% of patients revert to AF in spite ofantiarrhythmic drug treatment.¹ The usual clinical situation, then, isto maintain anticoagulation and ventricular rate control during chronicAF. The variable efficacy and frequent systemic adverse effects fromrate controlling drugs motivated our development of animal models ofgene transfer to control the heart rate in atrial fibrillation.

In porcine models of acute and chronic atrial fibrillation (AF), animalsunderwent coronary catheterization to deliver recombinant adenovirus tothe atrioventricular nodal region of the heart. Immediately prior tocatheterization, female domestic swine (30-40 kg) received sustainedrelease diltiazem 180 mg, aspirin 325 mg and sildenafil 25 mg orally,and a mixture of ketamine 100 mg and acepromazine 4 mg intramuscularly.(For uniformity, the same pretreatment regimen, except administration ofsildenafil, was used for all procedures to control for any effect theseagents might have on the baseline EP measurements.) After sedation,anesthesia was induced with 5-10 ml of intravenous sodium pentothal 2.5%solution and maintained with inhaled isoflurane 2% in oxygen. The rightcarotid artery, right internal jugular vein and right femoral vein wereaccessed by sterile surgical technique, and introducer sheaths wereinserted into each vessel. After baseline EP study, the right coronaryartery was catheterized via the right carotid artery, using a 7 Fr.angioplasty guiding catheter. The AV nodal branch was selected with a0.014″ guide wire, over which a 2.7 Fr. infusion catheter was insertedinto the AV nodal artery. Use following solutions were infused throughthe catheter: 10 ml of normal saline (NS) containing 5 μg of VEGF₁₆₅ and200 μg of nitroglycerin over 3 minutes, 1 ml of normal saline containing7.5×10⁹ pfu of AdGi or Adβgal and 20 μg of nitroglycerin over 30seconds, and 2 ml of normal saline over 30 seconds. After recovery fromanesthesia, the animals received usual care and no additionalmedication. After one week, repeat EP evaluation was performed; theanimals were sacrificed, and the organs were removed for histologicalevaluation.

Oral treatment with sildenafil and infusion of VBGF, nitroglycerin andcalcium-free solutions served to increase microvascular permeability andthus increase the efficiency of gene transfer. Using this deliverymethod, Western blot analysis demonstrated 600% overexpression ofGα_(i2) in the AdGi group when compared to untreated or Adβgal-treatedcontrols (FIG. 4A, p=0.01). The Adβgal-treated animals did not havesignificant differences in Gα_(i2) expression when compared tocontrols.²

After gene transfer, the heart rate was determined at the 1 weekfollow-up EP study for animals with acutely-induced AF, and heart ratewas determined daily for animals with chronic AF. The acute AF modelemulates the human condition of paroxysmal AF. In the acute AF model,Heart rate during acutely induced atrial fibrillation was decreased by20% in the AdGi-treated animals and unchanged in the Adβgal-treatedanimals when compared to the untreated state (FIG. 4B, p=0.005 and AdGiand p=NS for Adβgal compared to baseline).² In the chronic AF model,heart rate in the AdGi group decreased by 35% 7-10 days after genetransfer. There was no change in heart rate in the Adβgal group. Thisexample shows that Gα_(i2) overexpression is capable of reducing heartrate by 20-35% in acute and chronic models of AF. By comparison,currently available drug therapies reduce heart rate by 15-30%, buttreatment is often limited by systemic side effects.

FIGS. 4A-B are explained in more detail as follows. FIG. 4A. Westernblot of AV nodal tissue demonstrates Ga_(i2) overexpression in theAdG_(i) infected animals. Lane 1 is 10 mg of Ga_(i2) control. Lanes 2,4, 6, 8 are from Adbgal-infected animals and lanes 3, 5, 7, 9 are fromAdG_(i)-infected animals. Analysis of the bands shows a 5±1-foldincrease in Ga_(i2) content in the AdG_(i) animals relative to theAdbgal-infected controls. FIG. 4B. Analysis of heart rate before and 7days after gene transfer. AdGi gene transfer reduces ventricular rate by20% during atrial fibrillation (p=0.005). No difference in heart ratewas observed after Adbgal exposure.

EXAMPLE 5 Treatment of Polymorphic Ventricular Tachycardia in CongestiveHeart Failure of the Long QT Syndrome

Sudden death in patients with congestive heart failure is a commonclinical occurrence. In most studies, roughly half of all heart failuredeaths were sudden in nature. Often, the associated arrhythmia ispolymorphic ventricular tachycardia (VT) leading to ventricularfibrillation and death. The type of VT seen in these patients is similarto that observed in patients with the congenital long QT syndrome.Studies of animal models have documented the similarities between thesetwo diseases on a tissue and cellular level. In both conditions,heterogeneous increases in the action potential duration (APD) have beena consistent finding. In heart failure, the APD prolongation correlateswith downregulation of several potassium currents: the transient outwardcurrent I_(to), the inward rectifier current I_(Kl), and the delayedrectifier currents I_(Ks) and I_(Kr). In the long QT syndrome,prolongation of the action potential correlates with mutation in one ofthe potassium or sodium channel genes. Either condition disrupts thebalance of inward and outward currents. predisposing the patient tomalignant ventricular arrhythmias. This balance can be restored by genetransfer-induced overexpression of potassium channels.

In a guinea pig model, animals underwent surgical injection of AdHERGand then were followed for changes in APD and QT.³ Adult guinea pigs(200-250 g) received metafane anesthesia. The abdominal wall was incisedin sterile surgical fashion. The diaphragm was fixated with forceps inincised in an anterior-posterior direction. The pericardium was fixatedand opened. The heart was fixated, and 0.15 ml of AdHERG containingsolution was injected into multiple sites in the left ventricular freewall. The incisions were closed and the animal was allowed to recover.After 3 days, the animals were sacrificed and the cardiac myocytes wereezymatically isolated. Using conventional patch clamp methods, APD andion channel currents were measured. In comparison to control animals,AdHERG-infected animals exhibited a 7-fold increase in I_(Kf) outwardcurrent and a 50% reduction in APD. See FIGS. 5A-B.³

FIGS. 5A-B are explained in more detail as follows. FIG. 5A. Comparisonof I_(Kr) current in the presence or absence of gene transfer-mediatedoverexpression of HERG. FIG. 5B. Photograph of an action potentialtracing from a cell overexpressing HERG.

EXAMPLE 6 Treatment of Atrial Fibrillation

The present example demonstrates therapeutic lengthening of the actionpotential

The cellular adaptive processes that occur with AF are completelydifferent than those seen with heart failure. During sustained AF, thereis a shortening of the APD and refractory period, essentially with lossof the plateau phase of the action potential (FIG. 6). Clinical andexperimental studies have shown a 70% downregulation of the Ca²⁺current, I_(Ca,L), and the transient outward current I_(to), to accountfor the observed changes in the AP morphology. The inward rectifier andadenosine/acetylcholine activated potassium currents (I_(Kl) andI_(K,Ach)) are upregulated. The end result of these changes is animproved ability of the atrial myocytes to sustain the rapid and chaoticimpulses characteristic of atrial fibrillation. This situation creates acycle where the rapid rate causes a shortened refractory period whichallows the continuation of the rapid rate, an idea that has been termed“AF begets AF”. The maladaptive nature of the ion channel alterationssuggests drat interrupting these changes on a molecular level is apotential treatment for AF.

FIG. 6 specifically shows changes in the atrial action potential afterprolonged atrial fibrillation. Reduction in the transient outwardcurrent, Ito, and the 1-type calcium current, ICa,l result in adecreased notch and plateau. A normal action potential is noted by thedashed line.

To evaluate the ability of potassium channel gene transfer to extend theplateau phase of the action potential, the guinea pig model illustratedin example 5 was used.³ Rather than injecting AdHERG to shorten theaction potential, AdHERG-G628S was injected. This mutant reduced theintrinsic HERG and extended the plateau of the action potential in acontrollable fashion. I_(Ks) current density was reduced by 80%, whichcaused a 17% increase in APD (FIGS. 7A-B).³ Observation of the actionpotential morphology shows that the increase in APD occurs by extensionof the plateau phase of the action potential. When applied to atrialfibrillation, this extension of the action potential would have aneffect similar to that of potassium channel blocking drugs and reducethe occurrence of atrial fibrillation. Since the gene transfer-mediatedincrease would be specific to the atria, it would eliminate theventricular proarrhythmic effects caused by antiarrhythmic drugs.

FIGS. 7A-B are explained in more detail as follows. FIG. 7A showscomparison of I_(Kr) current in the presence or absence of genetransfer-mediated overexpression of a dominant negative mutant of HERG.FIG. 7B. Photograph of an action potential tracing from a celloverexpressing the mutant HERG.

EXAMPLE 7 Construction and Use of a Biopacemaker

Patients who suffer heart block or other cardiac conduction systemdisorders require placement of as electronic pacemaker to maintainadequate blood flow. While this treatment is standard practice (about250,000 cardiac pacemakers are implanted annually in the US), it isexpensive ($45,000 10-year cost) and carries substantial risk(infection, pneumothorax, etc.). A potential application of theinvention is to increase automaticity of focal regions in the sinusnode, atria, atrioventricular node, His-Purkinje system or ventricles inorder to replicate the activity of the native pacemaker.

In proof of principle experiments, guinea pigs underwent surgicalinjection of AdcgiKir2.1AAA. After sufficient time for proteinexpression had elapsed, the cardiac myocytes were isolated and analyzedusing conventional electrophysiological techniques. Adult guinea pigs(200-250 g) received metafane anesthesia. A left lateral thoracotomy wasperformed in sterile surgical fashion. The aorta was isolated. A cannulawas passed through the LV apex into the proximal aorta. The aorta wascross-clamped and 0.15 ml of Kreb's solution containing AdKir2.1AAA wasinjected over 40 seconds. The cross clamp and cannula were removed; theincisions were closed, and the animal was allowed to recover. After 3days, the animal was sacrificed. The heart was removed and cardiacmyocytes were enzymatically isolated using conventional methods. Cellsinfected with the virus were identified by the presence of GFPfluorescence. No uninfected cells exhibited automaticity, while severalAdcgiKir2.1AAA infected cells displayed spontaneous, regularly occurringaction potentials. Examples of uninfected and infected cells aredisplayed in FIGS. 10A-B.

FIGS. 10A-B are explained in more detail as follows. FIG. 10A.Spontaneously occurring action potentials in guinea pig ventricularmyocytes expression Kir2.1AAA. FIG. 10B Induced action potential from acontrol myocyte. No spontaneous action potentials were observed incontrol cells.

The following materials and methods were used as needed in the foregoingExamples.

Adenoviruses-I. Adβgal was a gift; the vector contained the E. coli lacZ gene driven by the human cytomegalovirus (CMV) immediate earlypromoter. AdG_(i) was constructed using a previously reported method¹⁹.The vector included the full-length rat Gα_(i2) gene driven by the CMVpromoter. Virus stock expansion and quality control were performed aspreviously described⁴.

Gene Transfer Procedure. Immediately prior to catheterization, femaledomestic swine (30-40 kg) received sustained release diltiazem 180 mg,aspirin 325 mg and sildenafil 25 mg orally, and a mixture of ketamine100 mg and acepromazine 4 mg intramuscularly. (For uniformity, the samepretreatment regimen, except administration of sildenafil, was used forall procedures to control for any effect these agents might have on thebaseline EP measurements.) After sedation, anesthesia was induced with5-10 ml of intravenous sodium pentothal 2.5% solution, and maintainedwith inhaled isoflurane 2% in oxygen. The right carotid artery, rightinternal jugular vein and right femoral vein were accessed by sterilesurgical technique, and introducer sheaths were inserted into eachvessel. After baseline EP study (as described below), the right coronaryartery was catheterized via the right carotid artery, using a 7 Fr.angioplasty guiding catheter. The AV nodal branch was selected with a0.014″ guide wire, over which a 2.7 Fr. infusion catheter was insertedinto the AV nodal artery. The following solutions were infused throughthe catheter: 10 ml of normal saline (NS) containing 5 μg of VEGF₁₆₅ and200 μg of nitroglycerin over 3 minutes, 1 ml of normal saline containing7.5×10⁹ pfu of adenovirus and 20 μg of nitroglycerin over 30 seconds,and 2 ml of normal saline over 30 seconds. After recovery fromanesthesia, the mammals received usual care and no additionalmedication. After one week, repeat EP evaluation was performed; theanimals were sacrificed, and the organs were removed for histologicalevaluation.

Electrophysiological Evaluation. Immediately prior to gene transfer andone week afterward, the animals underwent electrophysiologicalevaluation. A 5 Fr. steerable quadripolar EP catheter was placed throughthe right internal jugular vein into the high right atrium; a 5 Fr.non-steerable quadripolar EP catheter was placed through the sameinternal jugular vein into the right ventricle, and a 6 Fr.non-steerable quadripolar EP catheter was placed through the rightfemoral vein into the His bundle position. Baseline intracardiacelectrograms were obtained, and electrocardiographic intervals wererecorded. Following standard techniques, the AVNERP was measured byprogrammed stimulation of the right atrium with a drive train cyclelength of 400 msec.

After baseline measurements were obtained, atrial fibrillation wasinduced by burst atrial pacing from a cycle length of 180 msecdecrementing to 100 msec over 30 sec. Three attempts were made usingthis induction protocol. If no sustained atrial fibrillation wasinduced, the atria were paced at an output of 10 mA and a cycle lengthof 20 msec for 15 sec. The latter protocol reliably induced atrialfibrillation. The first episode of atrial fibrillation lasting longerthan 12 sec was used for analysis. The median duration for atrialfibrillation episodes was 20 sec (range 14-120 sec). The heart rate wasdetermined by measuring R-R intervals during the first 10 seconds ofatrial fibrillation (average number of R-R intervals measured was 32 perrecording). After conversion back to sinus rhythm, 1 mg of epinephrinewas administered through the femoral venous sheath. Atrial fibrillationwas re-induced in the presence of epinephrine (median episode duration131 sec, range 20 sec-10 min), and the heart rate was again measured(average number of R-R intervals measured was 60 per recording). In thedrug-free state, all episodes of atrial fibrillation terminatedspontaneously. After epinephrine infusion, 4 episodes persisted for 10minutes and were terminated by electrical cardioversion.

Histological Evaluation. After euthanasia, the heart and sections oflung, liver, kidney, skeletal muscle and ovary were removed and rinsedthoroughly in PBS. The atrial and ventricular septa were dissected fromthe heart and frozen to −80° C. The remaining portions of the heart andother organs were sectioned; and alternating sections were used forgross or microscopic analysis. The sections for gross examination werefixed in 2% formaldehyde/0.2% glutaraldehyde for 15 minutes at roomtemperature, and stained for 6 hours at 37° C. in PBS containing 1.0mg/ml 5-bromo, 4-chloro, 3-indolyl-β-D-galactopyranoside (X-gal), 15mmol/L potassium ferricyamde, 15 mmol/L potassium ferrocyanide and 1mmol/L MgCl₂. After staining, the slices were fixed with 2%formaldehyde/0.2% glutaraldehyde in PBS at 4° C. overnight. The sectionsfor microscopic analysis were embedded in paraffin, cut to 7 μmthickness, stained with X-gal solution as above and counterstained withHematoxylin and eosin stains using traditional methods. β-galactosidaseexpression in the AV node was quantified by counting 100 cells inrandomly chosen high-power fields of microscopic sections through theregion.

Western Blot Analysis of Gα_(i2) Expression. To quantify Gα_(i2) geneexpression, Western blot analysis of Gα_(i2) protein expression wasperformed on cytosolic extracts of frozen AV nodal tissue (NovexSystem). Samples were normalized for protein content, andSDS-polyacrylamide gel electrophoresis of the normalized samples wasperformed on 4-12% gradient gels. Proteins were then transferred tonitrocellulose membranes (30V, 1 hr). Detection of protein was performedby sequential exposure to Western Blocking Reagent (BoehringerMannheim), a mouse monoclonal antibody against Gα_(i2) (Neomarkers, 1ug/ml, 2 hours), and goat-anti-mouse secondary antibody conjugated withhorseradish peroxidase (NEN, 1:10000, 30 min). Bands were detected withthe enhanced chemiluminescence assay (Amersham) and quantified using theQuantity One software package (BioRad).

Statistical Analysis. The data are presented as mean±s.e.m. Statisticalsignificance was determined at the 5% level using the student's t testand repeated measures ANOVA, where appropriate.

The following materials and methods were specifically employed inExamples 4-6, above.

Adenovirus vectors-II. Adβgal, AdGi, AdHERG, and AdHERG-G628S arerecombinant adenoviruses encoding β-galactosidase, wild-type Gα_(i2),wild-type HERG, and HERG-G628S—a mutant of HERG found in some long QTsyndrome patients. Gα_(i2) is the second isoform of the alpha-subunit ofthe inhibitory G protein, and HERG is a potassium channel. Expression ofthe mutant channels reduces the intrinsic current of the respectivechannel, and overexpression of the wild-type channel increases theintrinsic current. AdegiKir2.1AAA is a bicistronic adenoviral constructwith enhanced GFP and Kir2.1AAA genes connected by an IRES sequence. Byuse of the IRES sequence, a single ecdysone promoter is capable ofdriving expression of both genes. The Kir2.1AAA mutant replaces GYG inthe pore region with AAA, causing dominant negative suppression of Kir2.1.

All of the adenoviruses were created using standard methods. For Adβgaland AdGi, the CMV immediate-early promoter was used to drive geneexpression, and for AdHERG, AdHERG-G628S and AdegiKir2.1AAA expressionwas driven by the ecdysone promoter system. Any promoter capable ofdriving expression of the transgene would be suitable under mostcircumstances. Virus stocks were maintained in phosphate buffered salinewith 10% glycerol and 1 mM MgCl₂. Virus quality control includedwild-type virus assay, injections titre measurement by plaque assay, andtransgene expression measurement by Western blot and functional assayappropriate to the specific gene.

See also the PCT application PCT/US98/23877 to Marban E. for additionaldisclosure relating to polynucleotides used in accord with the presentinvention.

The following references (referred to by number throughout the text withthe exception of Examples 4-6) are specifically incorporated herein byreference.

-   1. MacMahon, S., Collins, R., Peto, R., Koster, R. & Yusef, S.    Effect of prophylactic lidocaine in suspected acute myocardial    infarction: an overview of results from the randomized, controlled    trials. JAMA 260, 1910-1916 (1988).-   2. Echt, D. et al. Mortality and morbidity in patients receiving    encainide, flecainide, or placebo. N Engl J Med 324, 781-788 (1991).-   3. Waldo, A. et al. Effect of d-sotalol on mortality in patients    with left ventricular dysfunction after recent and remote myocardial    infarction. Lancet 348, 7-12 (1996).-   4. Donahue, J. K., Kikkawa, K., Johns, D., Marban, E. & Lawrence, J.    Ultrarapid, highly efficient viral gene transfer to the heart. Proc    Natl Acad Sci USA 94, 4664-4668 (1997).-   5. Donahue, J. K., Kikkawa, K. Thomas, A. D., Marban, E. &    Lawrence, J. Acceleration of widespread adenoviral gene transfer to    intact rabbit hearts by coronary perfusion with low calcium and    serotonin, Gene Therapy 5, 630-634 (1998).-   6. Wu, H. M., Huang, Q., Yuan, Y. & Granger, H. J. VEGF induces    NO-dependent hyperpermeability in coronary venules. Am J Physiol    271, H2735-H2739 (1996).-   7. Muhlhauser, J. et al. Safety and efficacy of in vivo gene    transfer into the porcine heart with replication-deficient,    recombinant adenovirus vectors. Gene Therapy 3, 145-153 (1996).-   8. French, B., Mazur, W., Geske, R. & Bolli, R. Direct in vivo gene    transfer into porcine myocardium using replication-deficient    adenoviral vectors. Circulation 90, 2414-2424 (1994).-   9. Kass-Eisler, A. et al. Quantitative determination of    adenovirus-mediated gene delivery to rat cardiac myocytes in vitro    and in vivo. Proc Natl Acad Sci USA 90, 11498-11502 (1993).-   10. Kass-Eisler, A. et al. The Impact of Developmental Stage, Route    of Administration and the Immune System on Adenovirus-Mediated Gene    Transfer. Gene Therapy 1, 395-402 (1994).-   11. Eschenhagen, T. G proteins and the heart. Cell Biol Int 17,    723-749 (1993).-   12. Dessauer, C., Posner, B. & Gilman, A. Visualizing signal    transductance: receptors, G-proteins, and adenylate cyclases. Clin    Sci (Colch) 91, 527-537 (1996).-   13. Quinones, M. et al. Avoidance of immune response prolongs    expression of genes delivered to the adult rat myocardium by    replication defective adenovirus. Circulation 94, 1394-1401 (1996).-   14. Channon, K. et al. Acute host-mediated endothelial injury after    adenoviral gene transfer in normal rabbit arteries: impact on    transgene expression and endothelial function. Circ Res 82,    1253-1262 (1999).-   15. Lafont, A. et al. Thrombus generation after adenovirus-mediated    gene transfer into atherosclerotic arteries. Hum Gene Ther 9,    2795-2800 (1998).-   16. Cichon, G. et al. Intravenous administration of recombinant    adenoviruses causes thrombiscytopenia, anemia and erythroblastosis    in rabbits, J Gene Med 1, 360-371 (1999).-   17. Marshall, E. Gene therapy death prompts review of adenovirus    vector, Science 286, 2244-2245 (1999).-   18. Pauschinger, M. et al. Detection of adenoviral genome in the    myocardium of adult patients wall idiopathic left ventricular    dysfunction. Circulation 99, 1348-1354 (1999).-   19. Akhter, S. et al. Restoration of beta-adrenergic signaling in    failing cardiac ventricular myocytes via adenoviral-mediated gene    transfer. Proc Natl Acad Sci USA 94, 12100-12105 (1997).

The following references are also incorporated by reference. Eachreference is referred to by number only in Examples 4, 6, above.

-   1. Khand A, Rankin A, Kaye G, Cleland J. Systematic review of the    management of atrial fibrillation in patients with heart failure.    Eur Heart J 2000, 21:614-632.-   2. Donahue J K, Heldman A H, Fraser H, McDonald A D, Miller J M,    Rade J J, Eschenhagen T, Marbán E. Focal Modification of Electrical    Conduction in the Heart by Viral Gene Transfer, Nature Med 2000;    6:1395-1398.-   3. Hoppe U C, Marbán E, Johns D C. Distinct gene-specific mechanisms    of arrhythmia revealed by cardiac gene transfer of two long QT    disease genes, HerG and KCNE1. Proc Nat Acad Sci 2001; 98:5335-5340.

All references are incorporated herein by reference.

The invention has been described in detail with reference to preferredembodiments thereof. However, it will be appreciated that those skilledin the art, upon consideration of the disclosure, may make modificationand improvements within the spirit and scope of the invention.

1. A method for treating atrial fibrillation comprising administering tocardiac tissue of a mammal a therapeutically effective amount of apolynucleotide encoding KCNH2-G628S and/or a polynucleotide encoding aconnexin, wherein the KCNH2-G628S and/or connexin are capable ofmodulating an electrical property of the cardiac tissue, and wherein thepolynucleotides are expressed in the cardiac tissue of the mammalwhereby the atrial fibrillation is treated.
 2. The method of claim 1,wherein the connexin comprises connexin 40, 43 or a functional fragmentthereof.
 3. The method of claim 1, wherein the polynucleotides areoperably linked to the same or separate vectors.
 4. The method of claim1, wherein the electrical property is at least one of refractoriness,speed of conduction or spatial excitation pattern.